Several methods for the preparation of sodium trans-[tetrachlorobis(1H-indazole)ruthenate (III)] (also known as KP1339, NKP-1339, IT-139, and Na[RuIIICl4(Hind)2]) exist in the literature. For example, W. Peti et al, Eur. J. Inorg. Chem. 1999, 1551-1555 discloses the following synthesis scheme.

In this method, limited solubility of the tetramethylammoniumchloride salt results in a requirement for high volumes of solvent. Furthermore, there are toxicity concerns regarding the use of tetramethylammonium salts. An additional process is described in U.S. Pat. No. 8,362,266. This process provides a method of making the compound M-trans-[tetrachlorobis(1H-indazole)ruthenate (III)], wherein M is an alkali metal cation, said method comprising the steps of: (1) reacting, in an aqueous solution or a mixture of water and a first organic solvent which is water soluble, indazolium trans-[tetrachlorobis(1H-indazole)ruthenate (III)] with an inorganic salt of said alkali metal cation M, to form the compound M-trans-[tetrachlorobis(1H-indazole)ruthenate (III)] and an inorganic salt of indazole; and (2) extracting said indazole from said M-trans-[tetrachlorobis(1H-indazole)ruthenate (III)] with a second organic solvent which is not substantially water soluble. This method is summarized in the scheme below.

The method described above is effective; however, the need for the extraction step and related hold times may limit the effective batch size. Also, the purity of the compound is directly related to the length of time that the compound is in the basic, aqueous environment. Overall yields for this method are in the 20-35%. Therefore, a method that does not utilize an extraction process, avoids an aqueous basic environment, is high yielding and produces compound with high purity levels is highly desirable. Furthermore, a methodology that avoids extraction and large amounts of organic solvents is also desirable. A methodology primarily focused on precipitation followed by filtration would satisfy this need.